MPD47

jacklet

alright what gives?

MPD47

Oh, I just thought a datalog that showed the 951 at 18000+ RPM was interesting.

jacklet

yea-was the datalogger smoking crack or did you find a way to stuff an f1 motor on meth in your car?

MPD47

It's an electrical glitch that I'm trying to deal with right now, it's either a bad ground or a bad sensor (or so we think).

jacklet

is it picking up the tach signal at the coil or elswhere's?

Chris White

Since the Tec3 drives its own ignition system it is the other way around – it is driving the coil packs so the tach signal is derived internally.

I haven’t seen this before! The only other possibility is that there is some serious noise (electrical) begin picked up by the crank sensor/wiring. Mike – I will chat with Fred (Electromotive president) on Monday - lets see what he says!

Chris White

BTW – on a complexly different note – there were two (!) 944 roadsters at Watkins Glen. Roof completely cut off with 6” tall windshields. Interesting!

jacklet

didn't know you went standalone-shows how much i pay attention

reactor2

A 16-valve engine doesn't rev any higher than an 8-valve does it? Or is the idea that with 4 valves/cylinder the valves don't have to open as much, thus allowing the engine to rev higher before problems with the valve train occur?

Darwantae951

Isn't that issue called "valve float"? when the valve springs cant retract the valve quick enough to seal in the intake charge? Just sorting out my own knowledge, thanks!

-Darwin

SeaCay

Been thinking of doing this myself to allow more cockpit room. Did they start as Cabriolets or where they hatchbacks? If the latter, how did they seal up the tail end?

Chris White

I didn't bring my camera with me so I don’t have any pics – You can’t tell if they were cabs or coupes when they started, the rear metal was all custom stuff and the cages tied in the suspension a little.

As for valve float – the most common problem is the valves bouncing off the valve seats. The valves are closing so rapidly that the force of the stock springs is not enough to keep the valve from bouncing back open for a brief period.

16v heads can be made to survive at higher rpm due to the much lighter valves/lifters. Valve train weight is the main enemy of high rpm.

Chris White

Darwantae951

Ah, thanks for adding that! I almost had it. In our cars, at what RPM would valve float begin to occur??

-Darwin

Chris White

You can rev a stock 8v engine past 7k rpm and it will not hand grenade. You will see greatly accelerated valve guide wear and no real power gains unless you change the cam and turbo. The 951 was not designed as a high rpm engine.

Chris White